In cases where the body of an automobile has been deformed due to a collision or other reasons, the repair is usually done by either pounding out the dented portion from inside or pulling said portion from outside. However, as the method which calls for pounding out the portion from inside calls for removal of interior equipment prior to the repair, the operation is troublesome and takes a lot of time. Therefore, the method which calls for pulling out dented portions from outside is usually employed.
An example of conventional tools for this purpose, a sheet metal drawing tool disclosed in Japanese Patent Publication No. 29343/1986 is widely known. Referring to FIG. 10, the sheet metal drawing tool has at one end thereof a shaft B which is often called a bit and provided with an arc electrode A. The shaft B is attached to a casing D having a pair of levers C so that the shaft B works in the longitudinal direction by means of operating the levers C. The sheet metal drawing tool functions in such a manner that a dented portion of a sheet metal can be pulled out by connecting the power supply portion of a welding machine to a part of the shaft B via a cable E, flowing electric current to the arc electrode A, thereby welding the end of the electrode to the portion of the sheet metal, and operating the levers C in that state to pull up the shaft B in the direction along its length.
In order to pull up the electrode, it is common practice performed in such an occasion that the operation shaft having the electrode at its end is pounded upward with a hammer in fractional actions so that the impact of the pounding pulls up the dented metal portion with the electrode therebretween.
One of the methods widely employed for pounding an operation shaft with a hammer calls for providing a hammer with an insertion hole, inserting an operation shaft through the hammer, and hitting the operation shaft by sliding the hammer along the shaft. This method is very convenient, because the operation shaft can be hit precisely at desired locations with a desired amount of force simply by pulling the hammer upward without any complicated operation.
However, if the hammer is permanently attached to the operation shaft, such a structure is inconvenient in that it is necessary to carry or handle the tool always together with the hammer whenever the tool is transported or in other occasions where the hammer is not needed.
In order to overcome this problem, the applicants of the present invention had previously offered an invention (Japanese Application No. 84120/1997) wherein a hammer is removably attached to an operation shaft. Said previous invention, however, calls for providing a hammer at its open portion with teeth, and providing the operation shaft with indented portions adapted to respectively receive the teeth therein, wherein fitting and removal of the hammer may be done only at these portions where the teeth are engaged in or removed from the indented portions.